Lens for vehicle-headlights.



No. 631,996. v Patened Aug. 29, 1899.

.1. H. PITKIN.

LENS FOR VEHICLE HEADLIGHYS.

(Application filed June z, 1899.)

(No Model.)

INUEN'T'OR.

WITN E5555 UNITED STATES PATENT ()FFICE.

JULIAN H. PITKIN, OF CHICAGO, ILLINOIS.

LENS FOR VEHlCLE-HEADLIG HTS.

SPECIFICATION forming part of Letters Patent No. 631,996, dated August29, 1899.

Application filed June 21, 1899. Serial No. 721,313. (No model.)

To all whom it may concern.-

Be itknown that I, JULIAN H. PITKIN, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois,

have invented certain new and useful Improvements in Lenses forVehicle-Headlights; and I do hereby declare the following to be a full,clear, and exact description of the invention, such as will enableothers skilled in the 16 art to which it appertains to make and use thethe same time crossing the line of the riders vision.

My improved lens is primarily intended for use on )icycles where athoroughly illu minated path from the wheel to a distant point ahead isessential in order that the character of the road may be revealed toenable the rider to avoid obstruction and consequent danger of injury,though it maybe applied to any vehicle-headlight. It is desirable inorder 0 to secure the best results that the entire number of light-raysbe utilized and concentrated throughout the path to be illuminated,which in the ordinary bicycle-headlight lens is not the case. Theobjection to the ordinary lens 5 in use is that it illuminates a wideangle close to the wheel, While the road in front is left in darkness,thereby greatly diminishing the probability of revealing an obstructionin the road to be traveled. By my improved lens the road fromimmediately front of the wheel to a considerable distance ahead isthoroughly illuminated by a beam of light extending in alaterally-confined path, and any obstruction either close to or remotefrom the wheel is. quickly revealed. Thesedesirable results are securedby constructing the lens of vertical and horizontal prisms, the anglesof refraction of the latter being made to vary from the top to thebottom of the lensthat is, each horizontal prism has a uniformref'racting-surface of different angle from that u! other horizontalprisms, whereas the vertical prisms have each a refracting-surface whichin itself varies at different portions of the prism from top to bottomof the lens, all as will hereinafter more clearly appear.

In the drawings, Figure l is a vertical sec tion of the lens through thecenter thereof on line 00 m, Fig. 2. Fig. 2 is a front face view. Figs.3 and 4: are horizontal sections of the lens on lines A B and C D,respectively, of Fig. 2.

The lens is preferably rectangular,as shown in Fig. 2, though it may besix or eight sided or of any desired form, and is usually cast or moldedin one piece for convenience of manufacture.

In constructing this improved lens advantage is taken of the Well-knownproperty of the prism to deflect a ray of light as it passestherethrough first toward the normal of the incident surface and then asit passes from the dense medium of the prism into the less dense airaway from the normal of the emergent surface. The direction of any rayof light may thus be controlled by changing the angle of the prismthrough which it is caused to pass.

In the drawings the lens E, shown preferably as rectangular in shape,has any usual form of center S, either plane or convex, and is providedwith horizontal prisms a, a, a a a and a and with vertical prisms b 19'12*. The number of horizontal and vertical prisms may of course bevaried either more or less than those shown.

B-ythe terms angle and inclination as used in the specification I meanthe angle between the incident and emergent surfaces or the inclinationof such surfaces to each other.

The horizontal prisms a, a, a a a and a are constructed to have theemergent surface ff of each at a different angle from that of the otherhorizontal prisms, and this variation of angles is graduatedsuccessively from the top to the bottom of the lens in regularorder-that is, the lower prism a has its surface f f of very slightinclination, so that a ray of light from. the source L striking theincident surface a e of the lens at I will be refracted as it emerges atZ from the dense medium of the prism and intercept the ground in thedirection of Z a few feet only ahead of the wheel. The prism a is madewith a path of uniform Width from the wheel to the each of the verticalprisms constantly varies in angle fromthe bottom to the top tocorretravel before reaching the ground.

by varying the angle of the surface of each vertical prism uniformlyfrom top to bottom the lighted path is made of a uniform widththroughout.

' Where the vertical and horizontal prisms meet, they are joined by acurved or what may for convenience be termed a segmental prism, as at c,Fig. 2, and as the angles of the horizontal-and vertical prisms vary attheir point of meeting the segmental joining prism is constructed with avarying angle suited to harmonize at its points ofmeeting with theangles of the horizontal and vertical prisms. Thus no abrupt changetakes place in joining the two sets of prisms and the pencils or rays oflight are not interrupted and no dark areas are formed.

The lens when in place is preferably inclined slightly to the vertical,as indicated in Fig. 1, in order to secure the greatest illuminatingeffect upon the ground and prevent the rays from interfering in anymanner with the riders vision.

By angles of the prisms is meant the angle of the emergent surface tothe incident surface thereof, such last-nained surface 2 e being thesame for all the prisms;

' Having'thus described the invention, what Iclaim as new, and desire tosecure by Letters Patent, is

l. A lens for vehicle-headlights having a series of vertical prisms, anda series of horizontal prisms varying in angle from the bottom to thetop thereof the incidentsurface of such prisms being in substantiallythe same plane, substantially as described.

2. A lens for vehicle-headlights having a series of vertical prisms eachof which varies slightly greater angle of its emergent surface, so thata ray of light from L reaching the incident surface at Z will berefracted in the direction of Z to reach the ground a few feet ahead ofthe ray from prism a. Likewise the prism a is constructed with aslightly greater angle than the prism a, and for like reason itsrefracted ray Z will reach the ground a few feet ahead of that fromprism a, and so on regularly to the top of the lens. Each successiveprism has its angle slightly increased in order to throw its emergentray farther ahead, as prism a in direction of Z prism a in direction ofZ, and prism a in direction of 1'. The effect of this regular variationin the angles of the horizontal prisms is that the rays of lightemerging therefrom Will form a continuous path of light upon the groundfrom a point close to the wheel to many feet ahead without at the sametime crossing the riders vision.

The vertical prisms h b b are arranged on opposite sides of the center Sand are designed to refract the rays so as to produce a parallel beam oflight where the rays intersect the ground, to thereby form a lighteddistant point reached by the upper horizontal prism. To this end theretracting-surface (Z d of each vertical prism varies in angle atdifferent parts thereof, and this for the reason that the rays refractedby such prisms reach the ground at varying distances from the lens.

The ray of light emerging from the lower portion of the vertical prismis to reach the ground at a point in close proximity thereto, for whichreason the angle of the prism at its lower part is slight, whereas theray from the upper part of the same vertical prism is to reach theground many feet away, and therefore the angle of the prism at that partis greater. This feature is well shown in Figs. 3 and 4. Fig. 3represents -a section of the vertical prisms near the tops thereof online A B, Fig. 2, and, as will be noticed, the angle of the emergentsurface 02 d of each of said vertical prisms is much greater than theangle of the same surface nearer the ground, as shown in Fig. 4, whichis a section on line C D of Fig. 2. In other words, the emergent surfaceof angle as between themselves fromthe bottom to the top of the lens,substantially as described.

3. A lens for vehicle-headlights having a series of vertical andhorizontal prisms, segmental prisms joining said vertical and horizontalprisms and having varying angles,substantially as described.

4. A lens for vehicle-headlights having horizontal and vertical prisms,segmental prisms joining the same, the varying angles of these prismsbeing so arranged that abeam of light of uniform width and extended foraconsiderable distance ahead is projected on the ground.

In testimony whereof I affix my signature in presence of two witnesses.

r, LIAN H. PITKIN. V5??- spond to the distance the ray of light has toIf the angles of the emergent surface of each of the vertical prismswere made uniform, the rays of light emanating from the lower portion ofthe vertical prisms would perhaps be of the. desired width near thewheel; but the upper portion of the prisms would contract the rays intoa much narrower path as their contact with the ground became moreremote,whereas in angle from the bottom to the top thereof, and a seriesof horizontal prisms varying in ICO

